Portions of this book appeared, in somewhat different form, in
_Astounding Science Fiction_ for August 1957 and _Analog Science
Fact & Fiction_ for April 1960.
All rights reserved. No part of this book may be reproduced or
transmitted in any form or by any means, electronic or mechanical,
including photocopying, recording, or by any information storage and
retrieval system, without permission in writing from the Publisher.
All the characters and events portrayed in this story are fictitious.
Published in the United States of America in 1970 by the Walker
Publishing Company, Inc.
Published simultaneously in Canada by The Ryerson Press, Toronto.